In a conventional data transmission of TV images, taking a video mode for example, the TV images are transmitted by interlacing fields. That is, each of the frames are divided into an odd field and an even filed, and the odd field only comprises pixels on odd lines of a frame, and the even field only comprises pixels on even lines of the frame. During the transmission, the odd field and the even field are alternately transmitted for the reason that data transmission amount can be reduced by a half. Therefore, an image data received at a receiving end is either the odd field or the even field rather than a complete frame, and the received image data needs to be de-interlaced to restore the completed frame to be displayed on an image display.
Under a film mode, 24/25 frames are outputted per second, which is different from a video frame of outputting 50/60 frames per second. FIG. 1a is a schematic diagram of a de-interlace processing of a conventional 2:2 pull-down film mode. At a TV transmitting end such as a TV station, via an interlacing, a first even field E1 and a first odd field O1 are generated from a first original frame P′1, and a second even field E2 and a second odd field O2 are generated from a second original frame P′2. The first even field E1, the first odd field O1, the second even field E2 and the second odd field E2 are transmitted in sequence to a TV receiving end such as a TV set. When the TV receiving end performs a de-interlacing, a first restored frame P1 is restored from the first even field E1 and the first odd field O1. 25 output frames per second of the film mode are converted to 50 output frames per second of the TV mode. Therefore, a first restored frame P1 is repeated again at a next output period. Accordingly, a second restored frame P2 is restored from the second even field E2 and the second odd field O2, and the second restored frame P2 is repeated at a next output period.
FIG. 1b is a schematic diagram of a de-interlace processing of a conventional 3:2 pull-down film mode. In this mode, 24 output frames per second of the film mode are converted to 60 output frames per second of the TV mode. A TV transmitting end performs an interlacing such that a first original frame P′1 forms into three fields E1, O1 and E1 in sequence, a second original frame P′2 forms into two fields O2 and E2 in sequence, and a third original frame P′3 forms into three fields O3, E3 and O3. The foregoing fields are then transmitted to a TV receiving end in sequence. When the TV receiving end performs a de-interlacing, a first restored frame P1 is restored from the fields E1 and O1. The 24 output frames per second of the film mode are converted to 60 output frames per second of the TV mode. Therefore, the first restored frame P1 is repeated twice to be respectively outputted at next two output times. A second restored frame P2 is restored from the fields O2 and E2, and is then repeated at a successive output time. A de-interlace processing of a third restored frame is the same as that of the first restored frame, a de-interlace processing of a fourth restored frame is the same as that of the first restored frame, and so on.
However, the foregoing method can not solve an undesirable affect from an object motion between successive frames. Take the 2:2 pull-down mode in FIG. 1a, and TV output images arranged as frame P1, frame P1, frame P2, frame P2 and so on for example. With respect to an output sequence, the first three frames P1, P1 and P2 have a same output interval between one another; however, when being recorded, the frames P1, P1 and P2 are not generated at a same interval. Therefore, when a motion object exists in a TV image, and the first three frames P1, P1 and P2 are displayed, jittering may occur when the second output frame is directly copied and outputted. The second output frame is preferably between the first output frame P1 and the third output frame P2 rather than being directly copied and outputted.
In recent years, liquid crystal display (LCD) technique develops very quickly, and a current LCD panel may output 100/200 frames per second. When a film mode is applied to the LCD capable of outputting 100/200 frames per second, 4 or 5 frames may be successively repeated so that obvious jitter (unsmooth visual effect) occurs. Therefore, a motion-compensating image processing circuit for frame rate conversion and a method thereof are provided according to the present invention, so as to overcome the foregoing disadvantage.